Friction type clutches are well known in the art. Friction type clutches generally comprise two discs. The first disc is more substantial and is usually the engine flywheel; the other disk is usually lighter and commonly referred to as the pressure plate. The flywheel is bolted to a flange on the end of the crankshaft, while the pressure plate slides axially on the output shaft. A spring mechanism is used to press the pressure plate against the flywheel.
In these general friction type clutches, engine torque is transmitted from the engine flywheel to the pressure plate by the friction between the two abutting forces. Because of this large amount of torque, the surface of the discs need to be formulated from a material having a high coefficient of friction, coupled with good wearing properties. The materials that are used to create these products often are too heavy and too expensive.
In other applications, clutch systems are used as part of a transfer case in a four-wheel drive vehicle. The transfer case transmits power (torque) to the front wheels of the vehicle from the rear wheels. The clutch is used to transmit this power from the rear input shaft to the front output shaft. The pressure plate applies the force to the clutch so that it engages and power is transmitted.
Methods and apparatus have been used to try to improve transfer case clutch systems and basic clutch systems in general. Some of these prior systems have tried to extend the life of the clutch disks, but they often proved to be too heavy and/or expensive.